Swapping of two numbers is a basic problem in programming, which requires the exchange of the values of two variables. This can be achieved in various ways, but one of the most popular techniques is to use a third variable to hold one of the values temporarily, which is then used to swap the values of the two variables. However, it is also possible to swap two numbers without using a third variable in C. In this article, we will discuss various techniques for swapping two numbers without using a third variable in C, along with code examples.
Before we dive into the techniques of swapping two variables without using a third variable, let us understand the basic concept of swapping. Swapping refers to the exchange of values between two variables. In the case of swapping two numbers, the value of variable A is exchanged with the value of variable B, and vice versa. This can be represented mathematically as follows:
A = A + B
B = A – B
A = A – B
The above mathematical formula can be used to swap two numbers without using a third variable. Now let us discuss various techniques for swapping two numbers without using a third variable in C.
 Using addition and subtraction: The first technique involves the use of addition and subtraction operators to swap two numbers. This technique is based on the mathematical formula we discussed earlier. Here is the code example for this technique:
int a = 5, b = 10;
a = a + b;
b = a – b;
a = a – b;
printf("After swapping, a = %d and b = %d", a, b);
Output: After swapping, a = 10 and b = 5
 Using multiplication and division: The second technique involves the use of multiplication and division operators to swap two numbers. This technique is based on the fact that multiplying and dividing a number by a nonzero value does not change its value. Here is the code example for this technique:
int a = 5, b = 10;
a = a * b;
b = a / b;
a = a / b;
printf("After swapping, a = %d and b = %d", a, b);
Output: After swapping, a = 10 and b = 5
 Using bitwise XOR: The third technique involves the use of bitwise XOR operator to swap two numbers. This technique is based on the fact that XOR of two same numbers is 0, and XOR of a number with 0 results in the same number. Here is the code example for this technique:
int a = 5, b = 10;
a = a ^ b;
b = a ^ b;
a = a ^ b;
printf("After swapping, a = %d and b = %d", a, b);
Output: After swapping, a = 10 and b = 5
 Using pointers: The fourth technique involves the use of pointers to swap two numbers. This technique is based on the fact that pointers store the address of a variable, and the address of a variable can be assigned to another pointer variable. Here is the code example for this technique:
int a = 5, b = 10;
int* ptr1 = &a, *ptr2 = &b;
*ptr1 = *ptr1 + *ptr2;
*ptr2 = *ptr1 – *ptr2;
*ptr1 = *ptr1 – *ptr2;
printf("After swapping, a = %d and b = %d", a, b);
Output: After swapping, a = 10 and b = 5
Conclusion:
Swapping two numbers without using a third variable is a basic problem in programming, which can be achieved using various techniques. In this article, we discussed four techniques for swapping two numbers without using a third variable in C, along with code examples. These techniques include the use of addition and subtraction, multiplication and division, bitwise XOR, and pointers. Each of these techniques has its own advantages and limitations, and the choice of technique depends on the specific requirements of the problem at hand. With the help of these techniques, programmers can achieve efficient and optimized code for swapping two numbers without using a third variable in C.
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Popular questions

What is swapping of two numbers without using a third variable in C?
Swapping of two numbers without using a third variable in C refers to the exchange of values between two variables A and B, without using any additional variable to hold the value temporarily. The aim is to swap the values of A and B directly, with the help of any mathematical or logical operations. 
Why is swapping of two numbers without using a third variable important in programming?
Swapping of two numbers without using a third variable is important in programming, as it helps to optimize the code and make it more efficient. By eliminating the need for an additional variable, it reduces the memory usage and also saves time in the execution of the program. 
What are the techniques for swapping two numbers without using a third variable in C?
There are various techniques for swapping two numbers without using a third variable in C, including using addition and subtraction, multiplication and division, bitwise XOR, and pointers. 
How does the bitwise XOR technique work in swapping two numbers without using a third variable in C?
The bitwise XOR technique involves using the XOR operator (^) to swap two numbers in C. It works by taking the XOR of the two variables A and B, storing the result in A. Then, taking the XOR of A and B again, storing the result in B. Finally, taking the XOR of A and B once more, storing the result in A. This results in the values of A and B being swapped. 
What is the benefit of using pointers in swapping two numbers without using a third variable in C?
Using pointers allows for direct access of the memory locations of the variables, which enables the values of A and B to be swapped without using a third variable. This technique is particularly useful when dealing with large data sets, as it reduces the memory usage of the program and speeds up its execution.
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